Vehicular engines are classed as an engine having cylinders arranged in series, an engine having cylinders positioned to oppose each other, a V-type engine having cylinders arranged in a V-shaped configuration, and the like.
Among the V-type engines, there is one type of engine in which primary and secondary side cylinder heads are placed respectively on primary and secondary side cylinder banks, thereby forming primary and secondary side engine banks. The cylinder banks are upper leg portions of a V-shaped cylinder block. In this engine, a primary side manifold-mounting flange for a primary side intake manifold is tightened to the primary side cylinder head by a plurality of primary side fasteners. The above intake manifold is provided with a plurality of primary side branch pipes for introducing inducted air into primary side cylinders of the primary side engine bank. A secondary side manifold-mounting flange for a secondary side intake manifold is secured to the secondary side cylinder head by a plurality of secondary side fasteners. The secondary side intake manifold is provided with a plurality of secondary side branch pipes for introducing inducted air into secondary side cylinders of the secondary side engine bank.
More specifically, a V-type engine 102 as illustrated in FIG. 7 is a multi-cylinder engine which includes, e.g., six cylinders. The engine 102 has primary and secondary side engine banks 104 and 106, respectively. The engine bank 104 is provided with three primary side cylinders (not shown). The engine bank 106 is provided with three secondary side cylinders (not shown). In addition, there is a V-shaped bank space 108 formed between the engine banks 104 and 106.
A primary side surge tank 112 is positioned above the secondary side engine bank 106. The surge tank 112 is formed in a primary side intake manifold 110. The surge tank 112 has the following branch pipes of the intake manifold 110 arranged in a side-by-side array: a primary side first branch pipe 114-1; a primary side second branch pipe 114-2; and, a primary side third branch pipe 114-3. The branch pipes 114-1 through 114-3 are connected at ones of distal ends thereof to a primary side manifold-mounting flange 116. There are primary side intake ports (not shown) which have the following portions formed at an upper portion of a primary side cylinder head (not shown): a primary side first port entrance portion 118-1; a primary side second port entrance portion 118-2; and, a primary side third port entrance portion 118-3. The above-mentioned flange 116 is located on the port entrance portions 118-1 through 118-3.
The flange 116, which extends along the port entrance portions 118-1 through 118-3, is fixedly attached to the primary side cylinder head by being fastened in a manner mentioned below. That is, the flange 116 is secured by: a primary side first fastener 122-1 at a primary side first flange end portion 120-1 on the first port entrance portion 118-1, the fastener 122-1 including a bolt and the like; a primary side second fastener 122-2 near the second port entrance portion 118-2; a primary side third fastener 122-3 near the third port entrance portion 118-3; and, a primary side fourth fastener 122-4 at a primary side second flange end portion 120-2 which continuously extends from a primary side communication portion 124 on the side of the third port entrance portion 118-3.
As illustrated in FIGS. 7 and 8, the aforesaid fasteners 122-1 through 122-4 are situated on a primary side port entrance centerline LC. The centerline LC interconnects respective centers of the port entrance portions 118-1 through 118-3, i.e., LO.sub.1 for primary side first center, LO.sub.2 for primary side second center, and LO.sub.3 for primary side third center.
A secondary side surge tank 128 is positioned above the primary side engine bank 104. The surge tank 128 is formed in a secondary side intake manifold 126. The surge tank 128 has the following branch pipes of the intake manifold 126 arranged in a side-by-side array: a secondary side first branch pipe 130-1; a secondary side second branch pipe 130-2; and, a secondary side third branch pipe 130-3. The branch pipes 130-1 through 130-3 are connected at ones of distal ends thereof to a secondary side manifold-mounting flange 132. There are secondary side intake ports (not shown) which have the following portions formed at an upper portion of a secondary side cylinder head (not shown): a secondary side first port entrance portion 134-1; a secondary side second port entrance portion 134-2; and, a secondary side third port entrance portion 134-3. The above-mentioned flange 132 is located on the above port entrance portions 134-1 through 134-3.
The flange 132, which extends along the port entrance portions 134-1 through 134-3, is fixedly attached to the secondary side cylinder head by being fastened in a manner described below. That is, the flange 132 is secured by: a secondary side first fastener 140-1 at a secondary side first flange end portion 138-1 which continuously extends from a secondary side communication portion 136 on the side of the first portion entrance portion 134-1, the first fastener 140-1 including a bolt and the like; a secondary side second fastener 140-2 near the first port entrance portion 134-1; a secondary side third fastener 140-3 near the second port entrance portion 134-2; and, a secondary side fourth fastener 140-4 at a secondary side second flange end portion 138-2 adjacent to the third port entrance portion 134-3.
As illustrated in FIGS. 7 and 8, the aforesaid fasteners 140-1 through 140-4 are located on secondary side port entrance centerline RC. The centerline RC interconnects respective centers of the port entrance portions 134-1 through 134-3, i.e., RO.sub.1 for secondary side first center, RO.sub.2 for secondary side second center, and RO.sub.3 for secondary side third center.
In this way, the flanges 116 and 132 are tightened respectively by the four primary side fasteners 122 and the four secondary side fasteners 140, all of which fasteners are linearly arranged along the respective centerline LC and RC. This is intended to both reduce the number of fasteners and insure sealing performance because the bank space 108 provides a low degree of freedom in the fastening of the two side intake manifolds 110 and 126.
A primary side distribution pipe 142 is connected at one end to the primary side surge tank 112. The other end of the pipe 142 is connected to a body side collection pipe 146 which continuously extends from a throttle body 144.
A secondary side distribution pipe 148 is connected at one end to the secondary side surge tank 128. The other end of the pipe 148 is connected to the body side collection pipe 146.
As shown in FIG. 7, the throttle body 144 is disposed at one end portion of the engine 102 within the bank space 108.
In addition, a thermo-case 150 is positioned at the other end portion of the engine 102 within the bank space 108.
Such an air suction device for a V-type combustion engine is disclosed in, e.g., published Japanese Utility Model Application Laid-Open No. 2-59253 and published Japanese Patent Application Laid-Open No. 6-50224. According to the former publication, right and left branch pipes for respectively distributing inducted air into right and left engine banks and two collectors for respectively collecting the right and left branch pipes are formed integrally. In addition, the branch pipes are integrally connected together at midway portions thereof. The collectors are fitted with respective throttle valves at entrance portions thereof. According to the latter publication, there are one intake pipe and another. The former pipe interconnects a surge tank on one side and a cylinder on the other side, while the latter pipe interconnects a surge tank on the other side and a cylinder on one side. These two pipes are alternately arranged to avoid an overlap on a plane, whereby the intake pipes are formed integrally as an intake pipe body. This body is provided with respective portions for mounting delivery pipes for supplying fuel to the downstream sides of the intake pipes. Further, head-fastening portions are provided adjacent to a downstream end of the intake pipe body. The fastening portions serve to fix the respective intake pipes to one cylinder head on one side and another on the other side. With continued reference to the above Japanese Patent Application Laid-Open No. 6-50224, tightening as illustrated in FIG. 9 is provided in order to improve sealing performance. In greater detail, the flange 116 is tightened by: two primary side second fasteners 122-2 near the primary side second port entrance portion 118-2, the fasteners 122-2 being symmetrically positioned on opposite sides of the primary side port entrance centerline LC; and, two primary side third fasteners 122-3 near the third port entrance portion 118-3, the fasteners 122-3 being symmetrically positioned on opposite sides of the centerline LC. Further, the flange 132 is secured by: two secondary side second fasteners 140-2 near the secondary side first port entrance portion 134-1, the fasteners 140-2 being symmetrically positioned on opposite sides of the secondary side port entrance centerline RC; and, two secondary side third fasteners 140-3 near the third port entrance portion 134-3, the fasteners 140-3 being symmetrically positioned on opposite sides of the centerline RC.
In conventional air suction devices for V-type combustion engines, a problem arises when components such as a throttle body and an ISC valve (an idle speed control valve) need to be assembled onto primary and secondary side intake manifolds. To be specific, when a component such as the throttle body is disposed within a bank space between primary and secondary side engine banks, respective locations for primary and secondary side fasteners to be secured thereat are hidden from view. In greater detail, when primary and secondary side manifold-mounting flanges are positioned adjacent to primary and secondary side port entrance centerlines, the above flanges lie near the longitudinal axis of the V-type engine. As a result, the flanges are hidden by the component such as the throttle body (such as body 144 as designated by slanted lines in FIG. 7). Consequently, the assembly of the mounting flanges is difficult to achieve. This results in an inconvenience in that the above two side intake manifolds must be respectively divided, with concomitant increases in both assembly time and cost.
Further, as shown in FIG. 7, a thermo-case 150 is disposed under the intake manifolds within the bank space 108. In addition, piping is provided at one end portion of the V-type engine. In this case, a thermo-case system must be laid out in a small gap between a chain case (a timing belt cover) and the intake manifolds. As a result, the gap under the intake manifolds is made extremely small when the flanges on both sides are tightened at positions adjacent to respective centerlines of the primary and secondary side port entrances. This causes an inconvenience by reducing the degree of freedom in the layout of the thermo-case system.
To eliminate the aforesaid inconveniences, the present invention provides an air suction device for a V-type engine, having primary and secondary side engine banks formed by primary and secondary side cylinder heads placed respectively on primary and secondary side cylinder banks, the cylinder banks being upper portions of a V-shaped cylinder block, in which a primary side manifold-mounting flange for a primary side intake manifold is tightened to the primary side cylinder head by a plurality of primary side fasteners, the primary side intake manifold being provided with a plurality of primary side branch pipes for introducing inducted air into primary side cylinders of the primary side engine bank, and in which a secondary side manifold-mounting flange for a secondary side intake manifold is secured to the secondary side cylinder head by a plurality of secondary side fasteners, the secondary side intake manifold being provided with a plurality of secondary side branch pipes for introducing inducted air into secondary side cylinders of the secondary side engine bank, the improvement wherein each end portion of the primary side flange is secured to the primary side cylinder head by a respective one of the primary side fasteners, whereas each end portion of the secondary side flange is fastened to the secondary side cylinder head by a respective one of the secondary side fasteners, and wherein at least one side of the primary and secondary side fasteners for respectively tightening the primary and secondary side flange end portions is disposed in an outward direction of the engine in relation to a respective port entrance centerline which interconnects respective centers of port entrance portions of the primary and secondary side intake ports, the intake ports being in respective communication with the primary and secondary side cylinders.
According to the present invention, the end portions of the primary and secondary flanges on both sides are positioned in the outward direction of the V-type engine with respect to the primary and secondary side port entrance centerlines. This arrangement enables the primary and secondary side intake manifolds having a throttle body and the like assembled thereon to be built into the V-type engine at a time without respectively dividing the intake manifolds. This feature allows for reductions in both assembly time and cost. Furthermore, components such as a thermo-case can be laid out with a greater amount of freedom. In addition, it is possible to reduce the likelihood that small components fall out and enter the bank space between the primary and secondary side engine banks.